The ballet isn’t generally known as a place for great humor, but Woody Allen was a cutup at the Youth America Grand Prix Gala, spies said. The “Annie Hall” director and wife Soon-Yi Previn were spotted there as guests at the David H. Koch Theater at Lincoln Center last week, along with David and Julia Koch, Wilbur and Hilary Ross, Debra Black and Karen LeFrak, who composed the score for a premiere of Marcelo Gomes’ dance piece “Tous Les Jours.” When the well-heeled group filed in for dinner after the performance, Allen was seen desperately scanning the place cards at his table. “I like it when Soon-Yi’s at the same table,” he explained to a guest, relieved to find she was seated nearby. When a party photographer asked to snap a pic, Allen quipped that he’s always happy to pose because, “It keeps me from eating.” And when a guest exclaimed Allen hadn’t changed since they’d met 35 years before, the director put his hand on his heart, tapped his chest and concluded, “No maturity.”